Current approaches to the use of generic antiepileptic drugs

Effects of generic exchange of solid oral dosage forms in neurological disorders: a systematic review

Background Generic drug exchange is common practice in most healthcare systems. While generics certainly contribute to economic savings, the altered drug formulation might be associated with potential therapeutic problems. Given the narrow therapeutic windows in neurologic indications, any detrimental effect on the therapy can lead to significant consequences. Aim of the review This review aims to investigate potential problems related to a switch from brand-name to generic or from generic to generic drug products in patients with neurologic diseases. Method The review was conducted following the PICO framework and the PRISMA guidelines. MEDLINE and Scopus databases were searched for articles published in English and German language between January 1, 1995 and October 17, 2018. Studies included in this review were randomized controlled studies, reviews, systematic reviews, overviews, cohort studies and case-control studies. Studies excluded were letters, comments, authors view, congress or seminar papers and studies with a focus on economic impact or costs. Results were synthesized qualitatively. The primary outcomes were pharmacokinetic parameters such as the area under the curve (AUC), the peak serum concentration (c_max) or the time at which c_max is observed (t_max). Results The search identified 67 studies with a great variety of endpoints and study designs. The leading indication was epilepsy. Two small RCTs were found on lamotrigine switch. Analysis of the other studies found no significant differences in pharmacokinetic parameters when switching to generic drugs. A more heterogeneous picture was revealed regarding hospitalizations, breakthrough seizures, failure of therapy, adherence and patient concerns. Conclusion While most reports were of poor quality, lamotrigine was the drug with the best available data. Summarizing the results of the available studies, pharmacokinetic parameters of antiepileptic drugs show low deviation. In contrast, data on clinical parameters are less consistent. Some studies found increased seizure frequencies and adverse-drug events, while others showed no complications. Adherence and patient satisfaction seemed to be impaired. In daily practice, generic exchange in epilepsy should be a carefully balanced decision, conducted with great caution. Further research is needed, especially regarding neurologic indications other than epilepsy.

Which information on women's issues in epilepsy does a community pharmacist need to know? A Delphi consensus study

OBJECTIVE

The aim of this study was to develop and achieve consensus on a core list of important knowledge items that community pharmacists should know on women's issues in epilepsy.

METHODS

This was a consensual study using a modified Delphi technique. Knowledge items were collected from the literature and from nine key contacts who were interviewed on their views on what information community pharmacists should have on women's issues in epilepsy. More knowledge items were suggested by five researchers with interest in women's issues who were contacted to rate and comment on the knowledge items collected. Two iterative Delphi rounds were conducted among a panel of pharmacists (n=30) to achieve consensus on the knowledge items to be included in the core list. Ten panelists ranked the knowledge items by their importance using the Analytical Hierarchy Process (AHP).

RESULTS

Consensus was achieved to include 68 knowledge under 13 categories in the final core list. Items ranked by their importance were related to the following: teratogenicity (10.3%), effect of pregnancy on epilepsy (7.4%), preconception counseling (10.3%), bone health (5.9%), catamenial epilepsy (7.4%), menopause and hormonal replacement therapy (2.9%), contraception (14.7%), menstrual disorders and infertility (8.8%), eclampsia (2.9%), breastfeeding (4.4%), folic acid and vitamin K (5.9%), counseling on general issues (14.7%), and sexuality (4.4%).

CONCLUSION

Using consensual knowledge lists might promote congruence in educating and/or training community pharmacists on women's issues in epilepsy. Future studies are needed to investigate if such lists can improve health services provided to women with epilepsy (WWE).

Association between switching antiepileptic drug products and healthcare utilization: A systematic review

AIMS

There is ongoing concern whether switching between different antiepileptic drug (AED) products may compromise patient care. We systematically reviewed changes in healthcare utilization following AED switch.

METHODS

We searched MEDLINE and EMBASE databases (1980-October 2016) for studies that assessed the effect of AED switching in patients with epilepsy on outpatient visits, emergency room visits, hospitalization and hospital stay duration.

RESULTS

A total of 14 articles met the inclusion criteria. All were retrospective studies. Four provided findings for specific AEDs only (lamotrigine, topiramate, phenytoin and divalproex), 9 presented pooled findings from multiple AEDs, and 1 study provided both specific (lamotrigine, topiramate, oxcarbazepine, and levetiracetam) and pooled findings. Three studies found an association between a switch of topiramate and an increase in healthcare utilization. Another three studies found that a brand-to-generic lamotrigine switch was not associated with an increased risk of emergently treated events (ambulance use, ER visits or hospitalization). The outcomes of the pooled AED switch studies were inconsistent; 5 studies reported an increased healthcare utilization while 5 studies did not.

CONCLUSION

Studies that have examined the association between an AED switch and a change in healthcare utilization report conflicting findings. Factors that may explain these inconsistent outcomes include inter-study differences in the type of analysis undertaken (pooled vs individual AED data), the covariates used for data adjustment, and the type of switch examined. Future medical claim database studies employing a prospective design are encouraged to address these and other factors in order to enhance inter-study comparability and extrapolation of findings.

Potential problems and recommendations regarding substitution of generic antiepileptic drugs: a systematic review of literature

Despite the availability of generic antiepileptic drugs (AEDs), still patients and neurologists hesitate to make a switch due to assorted reasons. The objectives of this review were to evaluate the risks associated with the generic substitution of AEDs. In this context, we also summarized the recommendations of various international societies to treat epileptic patients. We used a number of electronic databases to identify the relevant published studies which demonstrated the potential problems and recommendations regarding generic substitution of AEDs. Of 204 articles found initially, 153 were selected for additional review. Subsequently, 68 articles were finally selected. This review concluded that potential problems linked with the generic substitution of AEDs could be bioequivalence issues, failure of drug therapy, emergence of adverse events and increase in the frequency of seizures. The reasons could be the pharmacokinetics properties of AEDs and unique characteristics of some epilepsy patients. Consequently, the generic substitution of AEDs affects the successful treatment and quality of life of the patients. Various guidelines recommend the well-controlled epileptic patients to avoid switching from brand-to-generic products, generic-to-brand products or generic to some other generic products.

Three-way, three-period, crossover bioequivalence study of single oral dose of three brands of 300 mg phenytoin sodium tablets marketed in India, on healthy Indian human volunteers

OBJECTIVE

To compare the bioavailability of two brands of phenytoin sodium tablets available in the Indian market using Eptoin™ as the reference.

MATERIALS AND METHODS

A randomized, assessor-blind, three-way crossover design study was carried out over a period of 6 months after approval from the Institutional Review Board (IRB). Twenty-two healthy male participants received a single oral 300 mg oral tablet of either of the formulations with a 2-week washout. Blood samples were collected predose and at regular intervals postdose. Plasma phenytoin levels were estimated by high-performance liquid chromatography. Calculation of Cmax, AUC0-t, and AUC0-∞ was done by the linear trapezoidal rule and 90-110% margin (90% confidence interval (CI)) was used to assess bioequivalence.

RESULTS

Twenty volunteers completed the study. It was seen that the log-transformed values of Cmax, AUC0-t, and AUC0-∞ of the test formulations were not within the specified limits.

CONCLUSION

Bioinequivalence of available phenytoin brands indicates that switching brands could lead to variations in blood concentrations and thus impact safety and efficacy. If a brand switch is done for any reason, stringent drug-level monitoring is advised.

Bioequivalent antiepileptic drug switching and the risk of seizure-related events

BACKGROUND

Older antiepileptic drugs (AEDs) are known to have a narrow therapeutic index. As a consequence, switching between bioequivalent AEDs remains controversial in the management of epilepsy. We investigated the association between A-rated switching of each class of currently available AED and emergent treatment for a seizure-related event.

METHODS

We used a case-control method and claims data from the 2010 to 2011 Truven Health MarketScan(®) Commercial Claims Database to estimate the risk of seizure following a medication switch. Cases and controls with an epilepsy diagnosis were identified by emergency/inpatient or outpatient visit claims, respectively. Cases and controls (N=9110) were matched 1:1 by age, epilepsy diagnosis category and seizure medication. The exposure was defined as a switch between A-rated AEDs during the 90 days prior to index date. Conditional logistic regression was used to estimate the association, adjusting for gender, baseline Deyo-Charlson Comorbidity Index (0, 1, 2, or 3+), region (Northeast, Central, South, and West), and total AED medications.

RESULTS

A switch between A-rated AEDs occurred in 1053 (23.2%) cases and 827 (18.1%) matched controls. The unadjusted and adjusted odds ratios of a seizure-related event for switching were 1.38 (95% CI: 1.25-1.52) and 1.27 (95% CI: 1.14-1.41), respectively. The independent risk of an event also increased with each category increase in the Charlson score (CCI=1: 1.17, 95% CI: 1.02-1.33; CCI=2: 1.33, 95% CI: 1.09-1.62; CCI=3+: 1.99, 95% CI: 1.64-2.41). Older AEDs had infrequent switches compared to newer agents and were not associated with events.

DISCUSSION

We found a modest association between AED switching and seizure-related events. Our analysis suggests that the behavior of switching alone may lead to seizure-related events regardless of the medication or type of switch. Other disease or environmental characteristics may contribute to this association. Based on these and other findings, health care professionals and patients should be cautious about switching bioequivalent AEDs.

Interchangeability among therapeutic equivalents of lamotrigine: evaluation of quality of life

Epilepsy is the most common serious neurological disorder worldwide. Approximately 70% of patients with epilepsy have their seizures controlled by clinical and pharmacological treatment. This research evaluated the possible influence of interchangeability among therapeutic equivalents of LTG on the clinical condition and quality of life of refractory epileptic patients. The study was divided into three periods of 42 days, and an equivalent therapeutic LTG randomly dispensed for each period (two similars - formulations A and B, and the reference product - formulation C). The mean dose of LTG was 5.5 mg/kg/day. The presence of side effects tends to have a greater deleterious effect on quality of life of refractory epileptics compared to variations in number of seizures or changes in plasma concentrations. The results showed that independently of the drug prescribed, interchangeability among therapeutic equivalents can negatively impact epilepsy control.

Generic Substitution of Antiepileptic Drugs: A Systematic Review of Prospective and Retrospective Studies

Objective:

To systematically review the literature on generic antiepileptic drugs (AEDs), evaluate the efficacy and safety of generic AED substitution, and perform pharmacokinetic (PK) analysis using the American Academy of Neurology (AAN) scheme to classify evidence.

Data Sources:

PubMed and Cumulative Index to Nursing and Allied Health Literature searches from January 1, 1980, to October 15, 2010, were performed using the search terms anticonvulsant, antiepileptic drug, carbamazepine, divalproex, ethosuximide, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, phénobarbital, Phenytoin, primidone, topiramate, valproate, valproic acid, and zonisamide; bioavailability, bioequivalence, bioequivalency, bioequivalent, and substitution; and generic.

Study Selection and Data Extraction:

Retrospective and prospective controlled studies of generic substitution of AEDs were included in the review. Non-English-language articles and uncontrolled clinical studies were excluded, Published articles were categorized using the AAN criteria for systematic reviews.

Data Synthesis:

We identified 156 articles. Of these, 20 met our inclusion criteria; 7 were retrospective studies, 6 were prospective studies in patients with epilepsy, and 7 were prospective studies in healthy subjects. All articles were rated Class I to Class III, using AAN criteria. The retrospective studies were categorized as Class III and showed a significant relationship between generic substitution and increased use of health care resources because of seizures or AED toxicity. Prospective studies were categorized as Class I, II, and III. Prospective studies in patients showed no differences between brand and generic drugs in PK parameters of bioequivalence. Three prospective studies in healthy subjects reported significant differences in maximum drug concentrations. Comparison of brand and generic drugs revealed no significant difference in seizure frequency; however, some prospective studies showed significant differences in PK parameters, primarily those not used for bioequivalence determinations.

Conclusions:

There is inconsistency between retrospective and prospective studies of generic AED substitution. The highest levels of evidence indicate that there should not be a problem with generic substitution, although some patients are more prone to problems with the generic products. Some evidence suggests that switches between multiple generic AED products in certain individuals may be problematic.

Comparison of dissolution profiles and serum concentrations of two lamotrigine tablet formulations

Objective: The aim of this study was to investigate the extent of variations in lamotrigine serum concentrations between two immediate-release tablet formulations. Data were compared with in vitro difference and similarity tests on dissolution profiles of the two formulations.

Methods: Dissolution characteristics of formulations A (reference) and B (test) were evaluated at three points spanning the physiologic pH range (pH 1.2, pH 4.5, pH 6.8). A model-independent approach of difference (f1) and similarity (f2) tests were applied to dissolution data. A clinical study was performed with 16 patients who were divided into two groups — one group received formulation A (n=9) and the other received formulation B (n=7). Lamotrigine steady-state concentrations were determined by high-performance liquid chromatography on a reverse-phase column.

Results: There were no statistically significant differences in lamotrigine serum concentrations between the two groups, although formulation B had slightly higher mean concentration values (formulation A: 3.97±4.1 μg/mL; formulation B: 5.78±2.7 μg/mL). Dissolution profiles of the two formulations were similar in the pH 1.2 dissolution medium; however, the dissolution profiles of formulation B were outside the dissolution limit (≥85% at 15 minutes) in the pH 4.5 and 6.8 dissolution media.

Conclusions: No significant changes in the serum concentrations of lamotrigine were seen between the two investigated formulations. There is no evidence to suggest that the differences in dissolution profiles at pH 4.5 and pH 6.8 affect the therapeutic efficacy of the formulations. It is evident that the doses of test formulation given to the patients were higher as a consequence of common assumption that generic products have a lower absorption rate, which is proven unnecessary in this study. This investigation was a pilot study and thus further investigations with a larger sample size are necessary to determine if there is a connection between dissolution profiles and the therapeutic effect of investigated formulations.

Determinants of generic drug substitution in Switzerland

BACKGROUND

Since generic drugs have the same therapeutic effect as the original formulation but at generally lower costs, their use should be more heavily promoted. However, a considerable number of barriers to their wider use have been observed in many countries. The present study examines the influence of patients, physicians and certain characteristics of the generics' market on generic substitution in Switzerland.

METHODS

We used reimbursement claims' data submitted to a large health insurer by insured individuals living in one of Switzerland's three linguistic regions during 2003. All dispensed drugs studied here were substitutable. The outcome (use of a generic or not) was modelled by logistic regression, adjusted for patients' characteristics (gender, age, treatment complexity, substitution groups) and with several variables describing reimbursement incentives (deductible, co-payments) and the generics' market (prices, packaging, co-branded original, number of available generics, etc.).

RESULTS

The overall generics' substitution rate for 173,212 dispensed prescriptions was 31%, though this varied considerably across cantons. Poor health status (older patients, complex treatments) was associated with lower generic use. Higher rates were associated with higher out-of-pocket costs, greater price differences between the original and the generic, and with the number of generics on the market, while reformulation and repackaging were associated with lower rates. The substitution rate was 13% lower among hospital physicians. The adoption of the prescribing practices of the canton with the highest substitution rate would increase substitution in other cantons to as much as 26%.

CONCLUSIONS

Patient health status explained a part of the reluctance to substitute an original formulation by a generic. Economic incentives were efficient, but with a moderate global effect. The huge interregional differences indicated that prescribing behaviours and beliefs are probably the main determinant of generic substitution.

Seizure outcomes following the use of generic versus brand-name antiepileptic drugs: a systematic review and meta-analysis

The automatic substitution of bioequivalent generics for brand-name antiepileptic drugs (AEDs) has been linked by anecdotal reports to loss of seizure control. To evaluate studies comparing brand-name and generic AEDs, and determine whether evidence exists of superiority of the brand-name version in maintaining seizure control. English-language human studies identified in searches of MEDLINE, EMBASE and International Pharmaceutical Abstracts (1984 to 2009). Randomized controlled trials (RCTs) and observational studies comparing seizure events or seizure-related outcomes between one brand-name AED and at least one alternative version produced by a distinct manufacturer. We identified 16 articles (9 RCTs, 1 prospective nonrandomized trial, 6 observational studies). We assessed characteristics of the studies and, for RCTs, extracted counts for patients whose seizures were characterized as 'controlled' and 'uncontrolled'. Seven RCTs were included in the meta-analysis. The aggregate odds ratio (n = 204) was 1.1 (95% CI 0.9, 1.2), indicating no difference in the odds of uncontrolled seizure for patients on generic medications compared with patients on brand-name medications. In contrast, the observational studies identified trends in drug or health services utilization that the authors attributed to changes in seizure control. Although most RCTs were short-term evaluations, the available evidence does not suggest an association between loss of seizure control and generic substitution of at least three types of AEDs. The observational study data may be explained by factors such as undue concern from patients or physicians about the effectiveness of generic AEDs after a recent switch. In the absence of better data, physicians may want to consider more intensive monitoring of high-risk patients taking AEDs when any switch occurs.

Generics and cost-effective prescribing in Belgium: does bioequivalence always translate in therapeutic equivalence?

As many other countries, Belgium has a policy to promote the use of generic pharmaceutical products. In order to protect consumers, these generic products must be demonstrated to be essentially similar to the previously approved product, typically an innovator product. The therapeutic equivalence of a generic and an innovator product is most commonly based on the demonstration of bioequivalence, i.e. clinically insignificant differences in the rate and extent of drug absorption usually assessed from pharmacokinetic measurements, in a normal and healthy population. This article reviews the bioequivalence requirements for generic products and examines whether bioequivalence always adequately substantiates therapeutic equivalence and interchangeability. Clinical practice has identified a number of drug classes for which generic substitution should be approached with caution. Current bioequivalence requirements are based on a measure of average bioequivalence. There are fears that use of this measure may be inappropriate in the case of a drug with a narrow therapeutic range or high intrasubject or intersubject variability. Under these circumstances, measures of individual and population bioequivalence are proposed to be more accurate than measures of average bioequivalence. Bioequivalence issues are discussed together more general concerns about generic drug substitution, such as differences in product and packaging appearance and differences in excipients.

Association between antiepileptic drug switching and epilepsy-related events

Switching between bioequivalent antiepileptic drugs (AEDs) in patients with epilepsy remains a concern because of possible untoward effects owing to a narrow therapeutic range. We investigated the association between switching A-rated AEDs and epilepsy-related events. We conducted a case-control study using claims from the MarketScan database. Cases were defined by an emergently treated epilepsy-related event with the primary diagnosis of epilepsy. Controls had an epilepsy outpatient office visit. Eighty-four of 757 (11.1%) cases and 147 of 2271 (6.5%) controls experienced an A-rated switch. The odds of an epilepsy-related event were 1.78-fold higher for switchers (95% CI 1.35 to 2.36) and, when adjusted for gender and total number of AED prescriptions filled, 1.57-fold higher (95% CI=1.17-2.10). Switching between A-rated formulations of AEDs is associated with an increased risk of emergently treated epilepsy-related events. These findings suggest that care should be taken when considering a switch between A-rated AEDs in patients with epilepsy.

Understanding patients' perspective in the use of generic antiepileptic drugs: compelling lessons for physicians to improve physician/patient communication

Background

Epilepsy is a condition in which consistency of treatment is paramount to successful management and for most patients, effective seizure control can be achieved. Given the severe consequences of even a single breakthrough seizure, patients should be afforded every opportunity to succeed on their given regimens.

Discussion

Some experts argue that global policy on generic antiepileptic drug substitution in epilepsy should be limited – occurring at the discretion of and with careful monitoring by the physician. While the debate continues, physicians still have daily responsibilities to their patients to help them best manage their epilepsy within the context of the current environment – the reality of which may involve switching to a generic antiepileptic drug or navigating various formulations between generics.

Summary

To provide context, this paper first reviews the main "hot button" issues fueling the ongoing generic debate, including a broad overview of the current state of the literature. The main goal however is to provide physicians with a patient perspective on generic antiepileptic drug use in epilepsy as a source of clinically useful, everyday advice to improve communication and increase patient self-advocacy, both of which are necessary for optimal patient outcome.

Patient perception of generic antiepileptic drugs in the Midwestern United States

OBJECTIVE

Concerns have been raised about the safety of switching from a branded antiepileptic drug (AED) to a generic AED. The goal of the study described here was to understand patients' experiences with generic AEDs in the Midwestern United States.

METHODS

A one-page, six-item survey was mailed to 356 patients to determine patients' awareness of the existence and their usage of generic AEDs.

RESULTS

Twenty-eight percent (27.8%) of respondents (N=179) reported breakthrough seizures they believed were a direct result of the switch from a brand to a generic AED, and 33.7% reported side effects due to the switch. Thirty-one percent (31.2%) returned to a brand-name AED as a result. Sixty-nine percent (68.8%) reported being unaware that some pharmacies switch to generic AEDs without a patient's or physician's consent, and 78.7% expressed concern over this.

CONCLUSION

A significant percentage of patients reported that generic AEDs were responsible for breakthrough seizures and increased side effects. A significant percentage of patients also reported switching back to a brand-name AED and expressed concern over pharmacies switching to generic AEDs without a patient's or physician's consent.

An assessment of patient and pharmacist knowledge of and attitudes toward reporting adverse drug events due to formulation switching in patients with epilepsy

A survey was developed to gather information from both patients with epilepsy and community pharmacists on the issue of antiepileptic drug (AED) formulation switching, which includes brand to generic, generic to brand, and generic to generic. Data were obtained from 82 patients (or parents of patients) with epilepsy and 112 community pharmacists. More than 92% of patients and 85% of pharmacists agreed that switching between forms of the same AEDs may cause an increase in seizures or adverse effects. More than two-thirds of our patient sample reported having problems with formulation switching; many also reported knowing other patients with problems. Just more than half (51%) of the pharmacists knew of patients who have described problems when they have changed AED formulations. Less than 50% of both populations knew that problems resulting from formulation switching should be reported as adverse drug events to the FDA. Not many pharmacists and far fewer patients use MedWatch to report these problems. We conclude that both patients with epilepsy and pharmacists are underinformed and underinvolved with reporting adverse drug events.